A reservation for a squirrel requires a genuine intention/intrest in purchase, but is not an obligation to buy.
When the squirrel is offered and a mutual agreement of purchase has been made, the reservation will become an obligation. In case the squirrel is not what you expected when the purchase takes place, you are free to cancel.
Cases where this holds are when the quality, health, color, weight etc. is not what we agreed upon or different from what was expected. Since this is a hobby I aim for what is best for us and the animal :)
Deposits are not required. I use reservations as a service on my side to ensure everyone gets a fair chance to get a squirrel.